Mica, Fluorite or Calcite

If your mineral comes off into thin sheets or in layers, then you have Mica! Biotite Mica is black, and Muscovite Mica is lighter coloured or clear.

Calcite comes in many colours but it is identified usually by its blocky rectangular cleavage. It also fizzes when vinegar is put on it.

Fluorite also comes in different colours and is sometimes mistaken for Calcite or Quartz. It can be identified by its pyramid shaped crystals or by not fizzing with vinegar which Calcite does.